1. Field of the Invention
This invention is directed to a novel process for preparing molybdenum (IV) dialkyldithiophosphates and to the novel oil-soluble compounds produced thereby and to lubricant compositions containing same.
2. Discussion of the Prior Art
The need for friction modifiers and antiwear agents in today's energy crisis is obvious. Such additives can significantly reduce fuel consumption in internal combustion engines. The use of molybdenum compound antiwear agents and friction modifiers is known in the art. U.S. Pat. No. 3,400,140 discloses the use of phosphomolybdates, U.S. Ser. No. 007,057, now U.S. Pat. No. 4,208,292, discloses phosphomolybdates prepared by reacting a dialkylphosphorodithioic acid with a metal of ammonium molybdate; it is also known that Mo(VI) compounds are effective as friction modifiers.
The reactions of oxomolybdenum complexes of bidentate sulfur ligands with hydrogen sulfide is a well known method for the preparation of sulfido molybdenum complexes via exchange of oxygen for sulfur. Such reactions have been applied routinely for the preparation of both terminal and bridging sulfido molybdenum complexes of dialkyldithiocarbamates (dtc); and dialkyldithiocarbonates (or xanthates, xan). W. E. Newton, J. L. Corbin and J. W. McDonald, J. Amer. Soc., 98, 5387 (1976). Newton, McDonald, and co-workers, ibid, recently reinvestigated the reaction of a series of dioxo-bridged molybdenum(V) dialkyldithiocarbamates with hydrogen sulfide. They observed that sulfidation reactions occurred in a stepwise fashion, depending upon severity of reaction conditions, and that complete sulfidation required phosphorus pentasulfide as reactant.
Others have described sulfidation reactions using molybdenum(VI) dialkyldithiocarbamates of the type MoO.sub.2 (dtc).sub.2 : ##STR1## Accordingly the invention embodied herein is believed by applicants to be novel in all its aspects.